Spectrum Sensing in Cognitive Radio - Fading, Diversity and User Cooperation By Sanjeewa P. Herath Examination Committee: 1. Dr. R.M.A.P. Rajatheva (chairman), 2. Prof. Kazi m. Ahmed, 3. Dr. Poompat saengudomlert. MASTER THESIS COMPETITION 18 TH May 2009

Wireless access & Cognitive Radio Wireless access – high demand – Every one with mobile phones – Demand: High speed internet, TV, on-line movie But, the available radio resource is very limited Advantages – High speed internet, bandwidth – Low cost – Not using additional resources – Good QoS, Routing implementation Conventional Licensed User (Primary User) Network Unlicensed User (Cognitive User) Access Solution: Allow cognitive user access ? PU 1PU 2 PU 3 idle CU 2 CU 1

How to Detect? Detection by Cognitive Users Measure the energy content – Can use in CDMA, 3G, Wi-Max, 4G/OFDMA etc – Guaranteed security to primary users – Cost effective, simple in structure, less hardware PU Transmits Energy/Power CU 2 CU 1

The objective IEEE – First cognitive radio standard – 90% detection reliability even when 0 dB signal-to- noise ratio (SNR) IEEE – First cognitive radio standard – 90% detection reliability even when 0 dB signal-to- noise ratio (SNR) PU CU WALLWALL WALL (2) LOW SIGNAL ENERGY (1) MULTIPATH PROPAGATION Very weak signal PU Base Station

Diversity Combining Concept – Multiple copies of the same signal – Combine them Concept – Multiple copies of the same signal – Combine them PU CU WALLWALL WALL (1) MULTIPATH PROPAGATION Very weak signal PU Base Station Remove Fading Effects

Contribution Analysis of communication systems is complex High chance of making mistakes Analysis of communication systems is complex High chance of making mistakes 1.Theoretical analysis – PDF approach (new) – MGF approach (new) 2.Simulation Model (new) 1.Theoretical analysis – PDF approach (new) – MGF approach (new) 2.Simulation Model (new) Solution: Two way analysis

Diversity Combining Detection with MRC diversity (Rayleigh, False alarm probability 0.1, u=1) Detection with MRC diversity (Rayleigh, False alarm probability 0.1, u=1) Two way analysis 0 dB

More Diversity Six different diversity techniques are proposed – Motivation: Less complex, low cost solutions Six different diversity techniques are proposed – Motivation: Less complex, low cost solutions Proposed schemes 1.Maximal Ratio (MRC) - 20% 2.Equal gain (EGC) - 16% 3.Square-law (SLC) - 12% 4.Square-law selection (SLS) - 10% 5. Selection (SC) - 11 % 6.Switch-and-stay (SSC) - 2% Proposed schemes 1.Maximal Ratio (MRC) - 20% 2.Equal gain (EGC) - 16% 3.Square-law (SLC) - 12% 4.Square-law selection (SLS) - 10% 5. Selection (SC) - 11 % 6.Switch-and-stay (SSC) - 2%

How far should we improve? Required improvement by other means

Cooperative Detection Concept – PU assists CU to detects its presence – Tolerate capacity by PU Concept – PU assists CU to detects its presence – Tolerate capacity by PU PU CU WALLWALL (2) LOW SIGNAL ENERGY Very weak signal PU Base Station Improve signal strength Algorithm based solution – Convex optimization Based on IEEE standard Algorithm based solution – Convex optimization Based on IEEE standard

Cooperative Detection (2 Subcarriers, AWGN N c i ={2,1}, N b i ={2,2}) Cooperative Detection (2 Subcarriers, AWGN N c i ={2,1}, N b i ={2,2}) Flexible Low Data Rate

Industrial Contribution 66% (out of 90%) is achieved – 30 % by energy detection – 20 % by diversity – 16 % by cooperation 66% (out of 90%) is achieved – 30 % by energy detection – 20 % by diversity – 16 % by cooperation The rest of 24% by CU cooperation Relax assumption – Channel estimation – User mobility The rest of 24% by CU cooperation Relax assumption – Channel estimation – User mobility Future Work

Contribution to Academia (7) 1)Sanjeewa Herath, Nandana Rajatheva,``Analysis of Equal Gain Combining in Energy Detection for Cognitive Radio over Nakagami Channels,“ IEEE GLOBECOM `08, pp. 1-5, Nov.-Dec. 2008, USA. 2)Sanjeewa Herath, Nandana Rajatheva, Chintha Tellambura,``On the Energy Detection of Unknown Deterministic Signal over Nakagami Channels with Selection Combining,“ IEEE CCECE `09, May 2009, Newfoundland, Canada. 3)Sanjeewa Herath, Nandana Rajatheva,``Analysis of Diversity Combining in Energy Detection for Cognitive Radio over Nakagami Channels,"Accepted for IEEE Int. Conf. ICC `09, Jun. 2009, Germany - to appear. 4)Sanjeewa Herath, Nandana Rajatheva, Chintha Tellambura,``Unified Approach for Energy Detection of Unknown Deterministic Signal in Cognitive Radio over Fading Channels,“Accepted for IEEE Int. Conf. ICC `09, Jun. 2009, Germany - to appear. 5)Sanjeewa Herath, Nandana Rajatheva, Poompat Saengudomlert, ``Primary and Cognitive User Cooperation in Detection,“ Submitted for IEEE GLOBECOM '09, Nov.-Dec. 2009, USA. 1)Sanjeewa Herath, Nandana Rajatheva,``Analysis of Equal Gain Combining in Energy Detection for Cognitive Radio over Nakagami Channels,“ IEEE GLOBECOM `08, pp. 1-5, Nov.-Dec. 2008, USA. 2)Sanjeewa Herath, Nandana Rajatheva, Chintha Tellambura,``On the Energy Detection of Unknown Deterministic Signal over Nakagami Channels with Selection Combining,“ IEEE CCECE `09, May 2009, Newfoundland, Canada. 3)Sanjeewa Herath, Nandana Rajatheva,``Analysis of Diversity Combining in Energy Detection for Cognitive Radio over Nakagami Channels,"Accepted for IEEE Int. Conf. ICC `09, Jun. 2009, Germany - to appear. 4)Sanjeewa Herath, Nandana Rajatheva, Chintha Tellambura,``Unified Approach for Energy Detection of Unknown Deterministic Signal in Cognitive Radio over Fading Channels,“Accepted for IEEE Int. Conf. ICC `09, Jun. 2009, Germany - to appear. 5)Sanjeewa Herath, Nandana Rajatheva, Poompat Saengudomlert, ``Primary and Cognitive User Cooperation in Detection,“ Submitted for IEEE GLOBECOM '09, Nov.-Dec. 2009, USA.

Contribution to Academia (7) 1)Sanjeewa Herath, Nandana Rajatheva, Chintha Tellambura,``Performance Analysis of Square Law, Switch and Stay Diversity Techniques for Energy Detection over Nakagami Fading Channel,” In preparation to be submitted to IEEE Transactions on Communications. 2)Sanjeewa Herath, Nandana Rajatheva, Chintha Tellambura,``Energy Detection of Unknown Deterministic Signal in Fading and Diversity Reception,”In preparation to be submitted to IEEE Transactions on Communications. 1)Sanjeewa Herath, Nandana Rajatheva, Chintha Tellambura,``Performance Analysis of Square Law, Switch and Stay Diversity Techniques for Energy Detection over Nakagami Fading Channel,” In preparation to be submitted to IEEE Transactions on Communications. 2)Sanjeewa Herath, Nandana Rajatheva, Chintha Tellambura,``Energy Detection of Unknown Deterministic Signal in Fading and Diversity Reception,”In preparation to be submitted to IEEE Transactions on Communications.

Thank You Master Thesis Telecommunication FoS, AIT 18 th May 2009